Can you discuss how functional programming differs from object-oriented programming?
As a senior software engineer, you should be intimately familiar with both object-oriented and functional programming. An interviewer will ask you this question to confirm that you are aware of the different types of programming and some of the languages used in each type. They expect you to be able to describe both the similarities and differences between these. They may also want you to state your preference for which type of programming you prefer or use regularly.
"I've used both functional and object-oriented programming in my previous jobs. Functional programming relies on immutable objects, while object-oriented programming takes advantage of the mutable state and in-place modification of objects within the code. Functional programs are structured so that inputs are used in calculations and result in the desired output. Functional programming relies on the function of the software. In contrast, object-oriented programming consists of classes, instances, and variables that the program can manipulate. These may be inherited or extended, thus simplifying the coding. Languages typically used in functional programming include Clojure, F#, Erlang, and Common Lisp. Object-oriented languages include Java, C, C, and others."
When answering this question, summarize each type of programming, describe the languages used, and talk about your experience with or preference for these. Your pre-interview research should have indicated the type of programming that the organization currently uses or prefers. Your answer can also reflect the best methodology for the products they create for either internal use or commercial sale.
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Anonymous Answer
The main difference is that functional programming works on stateless, immutable data whereas OOP uses mutable state data. Functional programming acts like a set of instructions that can be applied to an immutable dataset and the functions themselves do not cause side effects. Functional programming can be beneficial in that it can be quicker to write and requires less system resources to execute and allows for parallel programming. OOP on the other hand allows you to abstract your code into classes with clear expectations and allows child classes to inherit parent class attributes and functions thereby simplifying the code in the child class and making the test cases more simple. OOP also allows for the concept of Encapsulation to apply which can prevent unauthorized users from accessing key data.
Amanda's Feedback
Well said! You've explained the difference between the two as well as the benefits of each. If you've recently worked on projects that required you to choose between utilizing functional programming or OOP, explain why you chose each and how you applied it to the project. This helps to demonstrate that you have put your analytical mindset to work and make the appropriate choice based on the needs of the project.
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